Self-threading coupling unit



April 4, 1939. J'. N. ICE

SELF-THREADING C OUPLING UNIT Filed Nov. 23, 1937 .a Zz'g. 5

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I l m r @www Patented Apr. 4, 1939 y SELF-THREADING coUrLING UNIT JamesN. Ice, Wheeling, W. Va., assigner to Paul H. MicheL Wheeling, W. Va.

Application November 23, 1937, Serial No. 176,137

3 Claims.

'I'his invention is directed to couplings designed especially for use inconnection with thin walled piping and particularly the thin walledconduits required for electric wiring and the thin 5 walled copper pipeor tubing which is being rapidly adopted as standard.

` The authorities now require that in electrical installation the wiresbe carried in metal conduits in the form of pipe-like structure and inl0 connection with such requirement, a very serious difculty has arisenin connecting the meeting ends of the conduit sections. The connectorsmust present a rigid joint absolutely sealed against the admission ofwater and when it is taken into consideration that these conduits areand must necessarily be of thin wall, seldom if ever reaching athickness of one-sixteenth of an inch, the practical impossibility ofthreading the meeting ends of these conduits in the` usual way andapplying a connector of conventional form thereto will be at onceappreciated because the ,thickness of the wall precludes the formationof conventional threads Without extreme liability of cutting through theconduit or sov weakening it that the subsequent application of thecoupling isnot only of little rigidity but, more importantly, open toleakage from Without, with a resultant joint which would not passinspection.

The difficulties in providing this type of joint as heretofore proposedhave been so pronounced that such joint has been practically discardedand the coupling made by sweating or otherwise uniting the coupling tothe conduit ends, with i the result of materially increasing the timeand labor required for the installation and thereby materiallyincreasing its initial cost. Of course, it will be appreciated that thethreaded type of union is economical from the time and labor savingstandpoint as Well as the cost of material and presents the ideal jointfor this type of work if the objections can be satisfactorily overcome.

The primary object of the present invention, therefore, is the provisionof a coupling particularly designed for electrical conduits, which, inits initial application to the end of one section, is self-threadingwith respect to the section, is provided With a particular type ofthread which will not cause severe weakening or cutting through theconduit, and which, when applied incident to its self-threadingoperation, remains without adjustment or change to insure an intimatesealing relation with Ythe conduit. The coupling so provided is,ofcourse, double-ended, with one end adapted to be applied to one end ofthe conduit and self-threading the conduit duringsuch application, andthe other end to receive the mating end of the next section of conduitwhich is self-threaded as it ls applied to the coupling.

The invention is further designed as a coupling for the meeting ends ofcopper pipe or tubing which is being universally adopted for water andlike purposes incident to its resistance to rust or corrosion and,therefore, of much longer life than the conventional piping employed forthis purpose. This copper tubing or pipe is also of thin walledproduction primarily incident to a saving in cost of a heavy Walledproduction and the further fact that the inherent resistance of thematerial of the copper tubing or pipe ren- .ders the heavy walledproduction unnecessary. The coupling for this purpose is identical inall respects to the coupling for electrical conduits, varying only indiameter, and with the further provision of an element which completelyseals the meeting ends of the copper tubing or pipe against possibleleakage and at the same time seals the thread-interrupted spaces in thecoupling ordinarily provided for the jreception of the cuttingsof thethread cutters.

A further object of the invention is to adapt the principles of thecoupling to the thimble used for connecting the end of the electricalconduit to the junction box, the thimble having the self-threadingcharacteristics so that it may be applied to the end of the conduit andcut the necessary threads on the conduit as the coupling is advanced tomaintain a rigid connection between the thimble and conduit withoutliability of cutting through the conduit; and an essential feature ofthe thimble is the provision of means whereby 1 self-threading Lmovementof the thiml l the conduit is limited to prevent the free e'. of theconduit from projecting beyond the free end of the thimble underpossible careless or hurried operation, this limiting of the conduit inits movement through the thimble preventing the free end of the conduit,which usually presents sharp edges incident to its cutting into therequired length, from projecting beyond the free end of the thimble andthus possibly wearing away the insulation of the wires which projectbeyond this free end when the thimble is connected in the junction box.To this end and for this purpose, the free end of the thimble is 'alsorounded, presenting a. smooth surface which, if contacted by the wire,avoids any possibility of injuring the insulation.

A further object of the invention is the propossibility of cuttingthrough the wall of the 'conduit or pipe- A further object of theinvention isthe provision of a coupling formed with longitudinallyranging. thread-cutting lengths and intermuiiate channels to receivethecuttings. with the central portion of the coupling integrally formedwith a completely annular interior area which interrupts or eliminatesthe channelportions and thus prevents the possibility of anyseepage ofwater entering the ends of the conduits.

A further object of the invention is the provision of an independentwasher which may be applied to a coupling in which the channels betweenthe thread-cutting areas extend throughout the length of the coupling,with said washer provided with projections tting the channels and forcedunder pressure longitudinally. of the coupling to approximately acentral point to thus seal the `channel portions against the possibilitysuch water from reaching the meeting ends of the conduits. '.lhe use ofthis independent element, where the coupling is to be used forconnecting copper water or like tubing or pipes, provides an effectiveseal against leakage from the tubing or pipes and in this use the endsof this independent element are preferably directed inwardly to cause aflaring' oi.' the adjacent ends of the copper tubing or pipes as thecoupling is applied, thus further sealing the ends of the tubing orpipes and insuring a continuation of the water between such adjacentends of the tubing or pipes.

The invention is illustrated in the accompanying drawing, in which: 4

Figure 1 is a view in section showing the coupling applied to themeeting ends of electrical conduits, the ends of the conduits beingshown slightly spaced from their final position to illustrate theintermediate uninterrupted threaded section of the coupling. A

Figure `2 is a vertical section of the coupling unit.

Figure 3 is anend view ofthe same.

Figure 4 is a section of the unit showing the intermediate independentmember applied .for the purpose of preventing leakage, the showingillustrating the independent member as used for connecting copper tubingor pipes.

Figure 5 is a transverse section through the coupling with theindependent unit in position.

Figureisanedgeviewoftheunit.

Figure 'I is an elevation of the unit.

Figure 8 is an elevation of the junction box connecting thimble.

Figure 9 is a vertical sectional view of the same. Figure 10 is a topplan view.

Figure 11 is an enlarged sectional view showing the formation of thecutting teeth employed in the coupling.

'I'he coupling unit l is a tubular body exte- :riorly formed asangularly related faces 2 to pro- .vide for the application of a wrench.'I'he coupling is interiorly formed with a series of rows ofthread-cutting teeth 3, which will be hereinafter more particularlydescribed, the rows of teeth being 'interspersed with plain channels 4formed by broaching the tube in the usual manner. The coupling unit isdesigned for application to electric conduits, indicatedA at l, or tocopper tubingand pipe. the essential characteristie of which is that thewalls are very thin as compared with the usual piping. The unit isdesigned to be self-threadinginthat it cuts the threads on the meetingends of the tubing or conduit and for this purpose, the thread cuttersare of minute depth at the entrant ends of the coupling and graduallyincrease in depth toward the center of the coupling.

In the form shown in Figures 1 and 2, the central portion or the innersurface or the una, 1n-

stead of being formed with the particular row of thread cutters and theintervening plain channels, is formed with a threaded area 6 whichextends uninterruptedly throughout the full interior annular surface ofthe unit. The threaded portion l, which will be hereinafter termed thesealing portion, is thus formed of uninterrupted threads which, ofcourse. provide a continuation of the thread formation of the threadcutters l.

More importantly, however, this intermediate sealing portion serves tointerrupt or eliminate the channels' l, so that when the ends of thetubing 5 meet at the central portion of the coupling unit, the threadedportion 6 forms a cornplete seal for the ends of the conduit or tubingandi thus prevents any possibility of seepage into such conduit whichmight otherwisegreach the interior of the conduit or tubing through thechannels l. Of course, the thread-cutting elements and threaded portion6 are formed in the interior of the unit and then the unit is broachedfrom the respective ends to form the channels 4 of appropriate length.

In this connection, it is to be understood that the intermediate orsealing section 6, through which the channels l do not extend, may be ofany appropriate length relative to the length of the unit. Thus, forexample, the sealing section 6 may occupy one-third the length of theunit while the remaining vtwo-thirds, that is one-third on each side oi'the section B, provides the selfthreading function. 'I'he suggestion ofmaking the sealing section of one-third the length of the "unit ismerely to indicate that the function of this section is to afford acomplete seal and it is to be understood that the axial length of thesec- 'I tion 6 may be that determined for the particular coupling andits function.

In Figure 11, there is shown an enlarged view illustrating the formationof the teeth providing the thread cutters on the interior of thecoupling unit. It is to be noted that these teeth have their leadingedges 8' of greater inclination than their trailing edges 1 and that theordinarily l ing edge, there is a tendency to a more complete wedgingaction of the formed threads on the conduit with those on the unit thanwould be the case if the leading and trailing edges were at the sameinclination. Of course. the sealing section 6, which is of uninterruptedthread formation, provides the same type of thread as that described.

As an alternative form to the integral sealing section 6 of the unit,the invention contemplates the use of an auxiliary member 9 in the formof an annular ring or washer III having exterior projections IIcorresponding in number to those of the channels I in the unit, withportions I2 intermediate the projections to just overlie the surface ofthe thread cutters of the unit. 'This sealing element 9 is slightlyover-size with respect to the unit and is forced under pressurelengthwise the unit to a point approximately centrally of its length.'I'he projections Il completely seal the channels 4 within the areaoccupied by the element and as the ends of the conduit sections abut theedges of the element 9, it is impossible for seepage to enter the endsof the conduit sections because the only passage for such seepage isthrough the broached channels 4 and these are as completely closed inthe use of the independent sealing element as they are in connectionwith the integral sealingsection 6.

Where the unit is designed for coupling copper tubing or pipes for thepassage of fluid, it is preferred that the independent sealing element 9be used in connection with the unit I and that the end edges of theelement 9 be inwardly flared, as indicated at I3 in Figures 4 and 6. Asthe unit is coupled to the tubing or pipe, the ends of such therefore,it is impossible, particularly where the ends of the tubing or pipe passbeyond the seal broaches through the ared ends of the element, for anyof the flowing fluid to escape.

While the independent element 9, as used in connection with electricalconduits, has not been described as having the flared ends I3, it isunderstood that the flared ends may be provided on the sea-ling element9 even when used with electrical conduits, if found necessary.

The invention lends itself also with particular advantage to thethimbles usually employed for connecting the ends of electrical conduitsto junction boxes. Such thimbles are illustrated more particularly inFigures 8, 9 and 10. As shown, they comprise the conventional body I 4,having an angular head I5 for wrench application and an exteriorlythreaded wall I6 to receive a nut I1 for connecting the thimble to thejunction box. The thimble is provided with interior threadcuttingelements I8 exactly as in the unit I, the entrant end for the conduitbeing practically plain at I9 to provide for the entrance of theconduit, and the immediately adjacent threads being very ne and ofreduced height and gradually increased to the proper threading depth, asis necessary for the self-threading operation.

When the thimble is used with an electrical conduit, the thimble, whenapplied to the conduit and turned by a wrench, will cut the necessarythreads on the conduit to insure a substantial union between the thimbleand conduit, preventing relative endwise movement of the thimble and yetfacilitating its removal when necessary for r'epair or other purposes.Ordinarily, the section of conduit to which the thimble is to be appliedis more or less rough with sharp edges at the end to which the thimbleis applied incident to cutting the end of the conduit by a hack-saw orthe like to obtain the proper length. If there is no limit totheapplication of the thimble, it may happen that the thimble'will bethreaded so far onto the conduit that the roughened and sharp end oftheconduit will project beyond the trailing edge of the thimble. As thewiresextend through the conduit and beyond the same for connection inthejunction box, the presence of any roughened or sharp portions withwhichthe wires may come in contact will have a tendency to cut through thevinsulation of the Wires because of short or other dilculty requiringrepair.

In order to avoid this possibility, the end of the threaded wall I6 ofthe thimble is thickened to provide interio'rly of the thimble, at theend passed through the opening in the junction box, an abrupt shoulder2U and the free face of the thickened portion of the thimble wall isrounded, as at 2|. Obviously, the thimble is limited in its applicationto the conduit because the end of the conduit will eventually reach andcontact the shoulders when further threading movement of the thimble isprevented. Thus, the ends of the conduit can never project beyond thatend of the thimble through which the wires extend in completing theconnection. Therefore, the wires cannot possibly be affected by anyroughened or sharp end of the conduit and such wires are furtherprotected by the rounded surface 2I of the thimble proper.

The thread-cutting elements I8 in the thimble are separated by the usualchannel 22 similar to that employed in the coupling and thethreadcutting elements I8 are formed similar to that described inconnection with the illustration of Figure 11.

In applying the coupling for the meeting ends of sections of electricalconduit 5, one end of the coupling is rst placed on the end of onesection and turned by the application of a wrench, forming threads onthe conduit and advancing lengthwise the conduit. This is aself-threading operation and incident to the particular formation of thethread-cutting elements 3, as previously described, the operation of theself-threading movement requires materially less power than would anordinary thread-cutting function. Furthermore, the apexes of thethread-cutting elements are slightly flattened and thus there is` littleliability of these thread-cutting elements cutting through the thicknessof the conduit.

After the application of the unit to one conduit section, the adjacentconduit section is threaded into the unit, the self-threading operationis, of course, identical with that previously described, and thethreading operation of the unit on the one section of conduit and thethreading operation on the other section of the conduit into the unitare continued until the ends of the units abut, both having threadedconnection with the sealing section 6, where the integral sealingsection is employed, or the threading operation described is continueduntil the ends of the conduit meet either the straight or flared ends ofthe removable sealing element 9, if the latter is employed. Under bothcircumstances, the broached channels 4 are sealed beyond orsubstantially at the meeting ends of the conduit or the meeting ends ofthe conduit 4and removable sealing element 9. Exterior water or moistureis, therefore, prohibited from entering the conduit and one of theserious disadvantages of employing couplings as heretofore constructedis entirely avoided in this manner.

Where the unit Ais employed for connecting copper'tubing or pipes forconveying uid, the application of the unit is as previously described.In this use, however, the coupling is preferably provided with theremovable sealing element 9,

5 having its end edgesy flared as described. As the connection is made,the ends of the tubing or pipes to be united are outwardly flared bythe' inwardly flared ends of the element 9 and as this element l sealsthe breached channels 4, at least 10 throughout the axial length of theelement, leakage from the connection is impossible.

In the use o1' the thimble, the latter is threaded on the end oi theelectrical conduit, forming its own threads and providing an inseparableconnection except `through a threading movement. 'I'he application ofthe thimble is continued until the ends of the conduit bear against theshoulders and the thimble and connected end of the conduit are thuspassed through the end ot the 20 junction box and secured by theapplication ot vthe nut l1.

. It is to be particularly emphasized that the coupling unit and thimbleare designed for use with electrical co'nduits and copper tubing orpipe, the walls of which are necessarily,.as commercially produced, verymuch thinner'than are the walls of conventional'pipe. The coupling andthimble are formed with connecting elements 'particularly designed toform .a proper gripping thread on the parts to be connected withoutrequiring the application of suillcient power which of itself might tendto crush or rupture the conduit or copper tubing or pipe. Therefore, thethread cutters have the particular formation described and indicated inFigure 11.

By the flattened apexes. of the thread cutters, a

practically .lull thread-cutting operation is secured without theliability ot the otherwise sharpened edge cutting through the conduit or4d tubing or pipe.

Furthermore, the vcoupling unit is particularly designed with a view topreventing seepage into the union, where the coupling is used withelectrical conduits, or escape of the carried fluid,

45 where the union is used with copper tubing or pipe. 'I'his iseffectively secured by the integral sealing section 6 or by the use ofthe independent sealing element 9, as previously described. 'l'hematerial'employed in the coupling unit and in the thimble must, ofcourse. be such as to permit eilective handling and application, and thethread-cutting portions of such unit and thimble must, of course, be sohardened as to eilectively cut the desired threads in the parts withwhich they cooperate. Otherwise, and except as above speclilcallydescribed, no limitation is intended in 'any particular by any showingo! specific relation or sizes of parts or suggestions as to materialemployed.

What is claimed to be new is:

1. A self-threading coupling unit interlorly 'iormd with thread cuttersections and intervening channels, and means on the ,interior oi.' theunit for sealing the channels throughout a portion of their lengths,Vthe sealing means comprising an independent element formed withprojections to seat with a driving flt in the channels of the unit andhaving an axial length materially less than that of the unit.

2. A self-threading coupling unit interiorly formed with thread cuttersections andintervening channels, and means onthe interior of the unitfor sealingth channels throughout a portion of their lengths, thesealing means comprising an independent element formed with projectionsto seat with a driving ilt in the channels of the unit 'and having anaxial length materially less than that of the unit, the end edges of theelement being inwardly ared.

3. A self-threading coupling unit interiorly formed with thread cuttersections and intervening channels, and means on the interior oi the unitfor sealing the channels throughout a portion of their lengths, thesealing means comprising an independentA element formed with projectionsto seat with a driving t in the channels of the unit and having an axiallength materially less than that of the unit, the exterior surface ofthe element overlying the thread cutter sections and having an interiordiameter corresponding to that of the tubular elements to be connected.

' JAMES N. ICE.

